_TypeError (type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>'

Question

// To parse this JSON data, do
//
//     final plans = plansFromJson(jsonString);

import 'dart:convert';

List<Plans> PlansFromJson(String str) => List.from(json.decode(str))
    .map((x) => Plans.fromJson(Map.from(x)))
    .toList();
// ignore: non_constant_identifier_names
String PlansToJson(List<Plans> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class Plans {
  Plans({
    required this.id,
    required this.title,
    required this.details,
    required this.selectSubCategory,
  });

  int id;
  String title;
  String details;
  List<SelectSubCategory> selectSubCategory;

  factory Plans.fromJson(Map<String, dynamic> json) => Plans(
        id: json["id"],
        title: json["title"],
        details: json["details"],
        selectSubCategory: List<SelectSubCategory>.from(
            json["select_sub_category"]
                .map((x) => SelectSubCategory.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "title": title,
        "details": details,
        "select_sub_category":
            List<dynamic>.from(selectSubCategory.map((x) => x.toJson())),
      };
}

class SelectSubCategory {
  SelectSubCategory({
    required this.id,
    required this.subcategorName,
    required this.details,
  });

  int id;
  String subcategorName;
  String details;

  factory SelectSubCategory.fromJson(Map<String, dynamic> json) =>
      SelectSubCategory(
        id: json["id"],
        subcategorName: json["subcategor_name"],
        details: json["details"],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "subcategor_name": subcategorName,
        "details": details,
      };
}

List PlansFromJson(String str) => List.from(json.decode(str)) .map((x) => Plans.fromJson(Map.from(x))) .toList(); this line show the error _TypeError (type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable' how to fix this error and why this error repeated my projects lot of times and explain

Answer 1

json.decode(str)

I doubt that str is an json object, not an array. So json.decode(str) return a Map. I recommend you checkout retrofit library to auto handle json mapping.